The present invention relates to a system for controlling microfilm readers, and more particularly to a microfilm reader control system in which the desired frame is specified by depressing input keys and then automatically transported to the projection position.
Various readers for microfilms, especially for microfiches, having such an automatic film transport function have been proposed or provided as disclosed, for example, in U.S. Pat. Nos. 3,792,440 (Makoto Murakoshi), 3,841,747 (Donald C. Peroutky et al.) 3,870,413 (Joseph Goebel) and 4,033,684 (Shiro Toriumi et al.).
For use in microfilm readers of this type, there are many kinds of microfilms including those of generally accepted standards which vary in reduction scale, size, the number of frames contained, etc. It is therefore desired that one microfilm reader be usable for at least two kinds of microfilms, but many of conventional readers are each adapted for films of a particular kind only and are accordingly extremely inconvenient for the user.
MINOLTA CAMERA Co., Ltd., assignee of this invention, has already provided a microfilm reader which includes a control circuit as shown in FIG. 3 and is thereby made usable for a microfiche A (reduction scale: 1/24) containing 63 frames in 7 rows and 9 columns as seen in FIG. 1, and also for a microfiche B (reduction scale: 1/48) containing 270 frames in 15 rows and 18 columns as shown in FIG. 2. The control circuit includes a circuit comprising voltage divider resistors DR.sub.1 to DR.sub.17 connected in series for giving at divider terminals DT.sub.1 to DT.sub.18 divider signals of stepwise varying voltages as frame specifying signals corresponding in number to the maximum number of frames arranged in the direction of the rows of the films A and B (hereinafter referred to as "X direction") to move the films in this direction. With the film B having the larger number of frames, all the frames can be specified through the terminals DT.sub.1 to DT.sub.18, while the frames of the film A with the smaller frame number are specified through the terminals DT.sub.1 to DT.sub.9 with the other terminals DT.sub.10 to DT.sub.18 short-circuited by closing a short switch SS. (FIG. 3 shows the arrangement for specifying the frame column numbers arranged in X direction. The frame rows arranged in Y direction are specified by a substantially similar circuit, which therefore will not be described.)
The control circuit further includes a circuit comprising lock-type mechanical coupling switches CS.sub.1 to CS.sub.18 which are connected in series and connectable to the divider terminals DT.sub.1 to DT.sub.18 respectively and which are so adapted that when one switch is closed, another switch already closed is turned off. The desired divider signal is drawn off by selectively turning on the corresponding one of the switches CS.sub.1 to CS.sub.18, and is compared in a comparator CO with the output of a potentiometer PM which is coupled to a film carrier for emitting a signal indicating the present position of the film. Until the output of the comparator CO becomes zero upon the output of the potentiometer PM matching the divider signal, a carrier drive motor CM is driven positively or reversely to place the specified frame in position for projection by moving the film A or B.
On the other hand, as disclosed in the above-mentioned U.S. patents, microfilm drive control systems have been provided in recent years in which the drive means is controlled in response to input to a key device of the non-lock (self-return) type through a memory circuit comprising IC or LSI elements.
The use of IC, LSI or like elements appears promising for controlling mechanical apparatus for a wide variety of functions with ease and improved accuracy without necessitating a circuit of complex construction.
Such an electronic circuit, although thus advantageous if used, nevertheless involves difficulties in handling signals when a lock-type key device is used which has the same circuit as is shown in FIG. 3, so that when power is temporarily turned off and thereafter turned on, or when the magnification of projection is changed, the electronic circuit is unable to locate the film specifically unless a signal specifying the position of the film is fed to the memory circuit in one form or another. Consequently there is the need for the user to manually place the film in position, or to strike a special initial key, hence very cumbersome.
To specify the position of the film in such an initial state, it is most desirable to project an index frame provided on the film, but the conventional apparatus is extremely inconvenient since the user must locate the index frame manually or by striking a specific key every time power is applied or the magnification of projection is changed. Partly because only a few of conventional readers are adapted for use with at least two kinds of microfilms, none of the known readers are provided with means for specifying the position of the film upon changing the magnification.